The present invention relates to an (electro-)luminescence device utilized in copying machines, printers and display apparatus, e.g., as a backlight device for a display apparatus and a light source for illuminating an original in an image-reading apparatus.
Hitherto, as light-emission devices for converting applied electricity into light, there have been used, e.g., tubes and bulbs, such as incandescent lamps utilizing light emission caused by resistance heating and fluorescent tubes utilizing light emission caused by discharge in dilute gas, and semiconductor devices, such as light-emitting diodes (LED) utilizing light-emission caused by recombination of electrons and holes at pn-junctions formed in organic crystals. As indoor or outdoor illumination light sources, the tubes and bulbs have been most frequently used, but LEDs have been frequently used as indicators for various electronic appliances. Furthermore, recently, liquid crystal display apparatus equipped with fluorescent lamps as a backlight have been used as a display device for computers and portable display terminals. In addition to such usages directly exposed to human eyes, there have been frequently used functional devices, such as light sources for illuminating originals in image reading apparatus for facsimile apparatus and image scanners, and photo-writing heads in LED printers.
These light source devices have their own advantages and disadvantageous depending on their types. For example, the tubes and bulbs are suitable for emitting intense light by receiving a large electric power but are large in size and liable to be broken. Further, they are not suitable for usages requiring a high-speed responsiveness. On the other hand, LEDs can emit only relatively weak light but are advantageous in that they are small in size, have excellent reliability and have high-speed responsiveness.
While not being as popular as the above-mentioned light sources, there has been partially used an electroluminescence device wherein a thin film layer comprising a crystalline fluorescent substance is formed on a substrate by coating or vapor deposition and is supplied with an AC electric field via an insulating layer to cause luminescence. Such an electroluminescence device can be formed in a thin film on a substrate and is advantageous for usages for uniformly illuminating wide ranges or for providing a small-sized, particularly a thin, apparatus including a light source.
However, such an electroluminescence device has drawbacks that it can only emit weak light even lower than an LED and requires a difficult drive scheme requiring a relatively high AC voltage, so that it has not been a popular light source device.
On the other hand, in recent years, there has been developed an organic film luminescence device (also called an organic LED device), which is provided in a film on a substrate, provides high luminance and allows a DC drive.
FIG. 11 illustrates a representative organization (laminar structure) of such an organic LED device.
Referring to FIG. 11, an organic LED device includes a substrate 1100, an anode 1201 comprising a transparent electrode of indium tin oxide (ITO), a hole-transporting layer 1202 comprising an organic hole-transporting material, such as an organic diamine (of, e.g., formula (1) below), an electron-transporting layer 1203 comprising an organic electron-transporting material, such as tris(8-quinolinolato)aluminum (of formula (2) below) and a cathode 1204 of a substance having a low work function such as Al and/or Hgxe2x80x94Ag alloy, laminated in this order. 
When a voltage is applied between the anode 1201 and the cathode 1204, holes injected from the anode 1202 to the hole-transporting layer 1202 and electrons injected from the cathode 1204 to the electron-transporting layer, are re-combined to cause luminescence.
FIG. 12 illustrates a state of luminescence occurring in the organic LED device of FIG. 11.
Referring to FIG. 12, a portion denoted by A  schematically represents the luminescence caused by recombination of holes injected to the hole-transporting layer 1202 from the anode 1201 and electrons injected to the electron-transporting layer 1203 from the cathode 1204.
Such organic LED devices can emit various colors of luminescence, e.g., by using different organic materials for the hole-transporting layer 1202 or the electron-transporting layer 1203, by admixing another organic material into these layers, or by inserting a luminescence layer comprising another organic material between these layers.
However, according to a conventional organic LED device, the luminescence color is determined by organic materials constituting a luminescence part, so that pixels of respectively different luminescence colors have to be formed in a usage, like a full-color display, requiring independent control of different luminescence colors.
FIG. 13 illustrates a typical organization of such an organic LED device.
Referring to FIG. 13, the organic LED device includes a substrate 1100; a first pixel comprising an anode (portion) 1201 comprising ITO for the first pixel, a hole-transporting layer (portion) 1202 of an aromatic diamine (of formula (1)), an electron-transporting layer/luminescence layer 1203 of tris(8-quinolinolato)aluminum (of formula (2)) and a cathode 1204 of Al or Hgxe2x80x94Ag alloy, etc.; and also a second pixel comprising an anode (portion) 1401 comprising ITO, a hole-transporting layer (portion) 1202 of an aromatic diamine (of formula (1)), an electron-transporting layer/luminescence layer 1203 of a mixture of tris(8-quinolinolato)aluminum complex (of formula (2)) and a fluorescent substance (of formula (3) below), and a cathode 1404 of Al or Mgxe2x80x94Ag alloy. 
In the above-mentioned device, the first pixel emits green luminescence, and the second pixel emits red luminescence.
In the device, the respective luminescence layers 1203, 1403 and the respective cathodes 1204, 1404, have to be patterned into shapes of the respective pixels. Moreover, if the cathodes 1204 and 1404 of the adjacent pixels directly contact each other, or even in a single pixel, if the cathode 1204 (1404) directly contacts the anode 1202 (1401) or the hole-transporting layer 1202 (1402), phenomena, such as crosstalk and current leakage, undesirable for the device performances, are liable to occur, so that the mutually adjacent pixels have to be formed in sufficient separation from each other.
In this case, as different luminscence colors are emitted from different pixels, different color pixels are liable to be noticeable to human eyes by a careful observation, thus providing an unsatisfactory display quality.
When such an organic LED device is used as a light source for illuminating an original in an image reading apparatus, the directively of illumination light reaching a certain point on the original can be different for respective luminescence colors due to the fact that different luminescence colors are emitted from fairly separated different pixels, so that color irregularity is liable to occur depending on the surface gloss of the original.
In view of the above-mentioned problems of the prior art, a principal object of the present invention is to provide a luminescence device, particularly an organic LED device, having a minimized difference in sites for emitting different luminescence colors.
According to the present invention, there is provided, a luminescence device, comprising a substrate, and a laminated layer structure formed on the substrate including a plurality of luminescence layers emitting different luminescence colors, and a plurality of electrodes forming at least one pair of electrodes each sandwiching an associated luminescence layer, wherein at least one of the plurality of electrodes is provided with apertures, through which a luminescence flux emitted from at least one of the luminescence layers is caused to pass.
Each of the plurality of luminescence layers may comprise one or more organic compound layers. In the luminescence device, plural layers of electrodes each belonging to different pairs of electrodes sandwiching associated luminescence layers of different luminescence colors are respectively provided with apertures of which positions and/or sizes may be at least partially different from each other. Further, each pair of electrodes sandwiching an associated luminescence layer may comprise one transparent electrode on a side closer to the substrate and the other opaque electrode provided with apertures on a side more remote from the substrate, so that the luminescence flux is emitted through the substrate.
Further, at least: one luminescence layer may be sandwiched by a pair of electrodes which are both provided with apertures of which positions and/or sizes are at least partially different from each other so that the pair of electrodes comprises one transparent electrode on a side closer to the substrate and the other opaque electrode, and luminescence light flux is emitted in a direction leaving away from the substrate.
The present invention further provides an image-reading apparatus including a luminescence device as described above as an illumination light source, and a data processing apparatus including such an image-reading apparatus as a data-reading unit.
The present invention further provides a display apparatus including a luminescence device as described above as a display unit.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.